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Studying back EMFs in Spice

Discussion in 'CAD' started by Paul Burridge, Dec 16, 2004.

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  1. I've been messing about chopping the voltage supplied to an inductor
    in spice, hoping to see a sharp spike of x thousand volts as the
    magnetic field collapses. So far though, no joy. I can only imagine
    I've not contrived an appropriate circuit that would demonstrate the
    effect. Can anyone post a simple schematic that does illustrate this
    property of inductors?

    Thanks,

    p.
     
  2. Paul,
    This is the basis of "Boost" DC/DC converters. Below is an
    LTspice schematic doing this open loop.

    --Mike

    Version 4
    SHEET 1 1056 680
    WIRE 160 384 160 368
    WIRE 160 288 160 272
    WIRE 160 160 32 160
    WIRE 32 160 32 176
    WIRE 32 256 32 272
    WIRE 0 448 0 416
    WIRE 0 336 0 304
    WIRE 0 304 112 304
    WIRE 160 272 224 272
    WIRE 288 272 336 272
    WIRE 160 272 160 256
    WIRE 336 272 336 288
    WIRE 336 352 336 384
    WIRE 160 176 160 160
    FLAG 32 272 0
    FLAG 160 384 0
    FLAG 112 352 0
    FLAG 0 448 0
    FLAG 336 384 0
    SYMBOL ind 144 160 R0
    SYMATTR InstName L1
    SYMATTR Value 10µ
    SYMBOL sw 160 384 M180
    WINDOW 0 28 89 Left 0
    WINDOW 3 23 20 Left 0
    SYMATTR InstName S1
    SYMBOL voltage 32 160 R0
    WINDOW 3 27 94 Left 0
    SYMATTR Value 5
    SYMATTR InstName V1
    SYMBOL voltage 0 320 R0
    SYMATTR InstName V2
    SYMATTR Value PULSE(0 1 0 1u 1u 4u 10u)
    SYMBOL diode 224 288 R270
    WINDOW 0 32 32 VTop 0
    WINDOW 3 0 32 VBottom 0
    SYMATTR InstName D1
    SYMBOL cap 320 288 R0
    SYMATTR InstName C1
    SYMATTR Value 1µ
    TEXT 432 416 Left 0 !.model SW SW(Ron=.1 Roff=10Meg Vt=.5 Vh=--.4)
    TEXT 432 392 Left 0 !.model D D(Ron=1. Roff=10Meg)
    TEXT 430 364 Left 0 !.tran 10m
     
  3. Many thanks, Mike. I'll give it a try.
     
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